keep under one's hat


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keep (something) under (one's) hat

To not reveal or discuss something publicly. Keep this under your hat for now, but Greg is definitely the one getting the promotion.
See also: hat, keep
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

keep under one's hat

Preserve the secrecy of something, as in I'll tell you about it if you promise to keep it under your hat. This usage alludes to hiding a secret in one's head, covered by a hat. [Late 1800s]
See also: hat, keep
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

keep (something) under one's hat, to

To preserve secrecy. This term, with its vivid image of hiding a secret under headgear, dates from the late nineteenth century and has remained current even though hats are worn much less frequently today. A popular song of the 1920s had it: “Keep it under your hat! You must agree to do that. Promise not to breathe a word” (quoted by Eric Partridge). See also in the dark.
See also: keep
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
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